Airbus "TERRAIN…TERRAIN" & "TOO LOW, TERRAIN"
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Airbus "TERRAIN…TERRAIN" & "TOO LOW, TERRAIN"
Hi there
There is a line in the GPWS procedure (which is memory item in Airbus) that I don't fully understand.
In case of a "TERRAIN… TERRAIN" or a "TOO LOW, TERRAIN" alert from the GPWS, the procedure is:
"adjust the flight path or initiate a go around"
anyone can elaborate on this?
What is the procedure in BOEING?
cheers
There is a line in the GPWS procedure (which is memory item in Airbus) that I don't fully understand.
In case of a "TERRAIN… TERRAIN" or a "TOO LOW, TERRAIN" alert from the GPWS, the procedure is:
"adjust the flight path or initiate a go around"
anyone can elaborate on this?
What is the procedure in BOEING?
cheers
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Something like TCAS TA and RA, in GPWS you get caution and warning. Cautions are " Don't sink, Terrain ahead, obstacle ahead and too low flaps. Warnings are executive commands like " Obstacle ahead pull up, Terrain, Terrain pull up and Terrain ahead pull up. With a caution you have 60 seconds to impact and with a warning it is 30 seconds to impact. With a caution it may be possible to silence the caution by corrective actions like too low flap means you have not selected flaps full. Either selecting full or correcting GPWS and MCDU to 3 will silence it. Similarly after take off or GA if you start descending, which you are not supposed to it will caution you "don't sink" which will stop when you stop descent. But when warning is issued it is too late and immediate GA with TOGA power and full back stick must be initiated.
Something like TCAS TA and RA, in GPWS you get caution and warning. Cautions are " Don't sink, Terrain ahead, obstacle ahead and too low flaps. Warnings are executive commands like " Obstacle ahead pull up, Terrain, Terrain pull up and Terrain ahead pull up. With a caution you have 60 seconds to impact and with a warning it is 30 seconds to impact. With a caution it may be possible to silence the caution by corrective actions like too low flap means you have not selected flaps full. Either selecting full or correcting GPWS and MCDU to 3 will silence it. Similarly after take off or GA if you start descending, which you are not supposed to it will caution you "don't sink" which will stop when you stop descent. But when warning is issued it is too late and immediate GA with TOGA power and full back stick must be initiated.
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TOGA power and full back stick must be initiated.
Oh, wait, I guess you can do this in an Airbus and it will only kill you sometimes.
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As vilas said, if you get a warning you must apply TOGA and full back stick. In case of cautions there are several courses of actions according to the type of caution.
Furthermore if your airplane is equipped with the T2CAS function you might get some other warnings like the Avoid Terrain.
Furthermore if your airplane is equipped with the T2CAS function you might get some other warnings like the Avoid Terrain.
Airbus has optional fits for either EGPWS (Honeywell) or T2CAS (Thales). There should not be any major difference if both systems are certificated to the same standard (TSO-C151a).
The principle is that these systems provide boundaries for safe flight with an alerting (amber) awareness and a warning (red) commands. Amber level voice alerts are associated with amber lights, Red levels with a red light and where enabled, terrain-map pop-up depending on system type.
The red warning level requires executive action and is to pull-up wings level to establish the best rate of climb. Wings level has been subject to great debate, which in the early days of EGPWS involved all manufacturers, and the manoeuvre had to correspond with the terrain database/map accuracy. It is likely that as systems have developed, particularly with T2CAS, that in some circumstances a turn might be allowed, but always remember it is terrain (obstacles) that have to be avoided.
Amber cautionary alerting covers many scenarios and generally provides additional time for manoeuvre (but don’t depend on specific time values), - quickly evaluate the situation and adjust. Thus procedure wording can involve flight-path adjustment, climb, GA, turn, or change of configuration.
If a TERRAIN alert is given during an approach then a GA would be the better course of action as the EGPWS and procedures are designed such that alerts should not occur; if they do something is wrong and it is better to establish what at a safe altitude.
TERRAIN alerts at other times might be quickly resolved with flight path adjustment, but don't prejudge any situation assesment.
Other alerts during the approach such as Glide Slope or those involving Flap/Gear, might be subject to operator procedures, but in general the better option is to climb to provide time for evaluation.
Never try to second guess the situation; EGPWS reliability is now significantly better than the rate of human error – EGPWS is an error detector, yours or someone else’s.
The principle is that these systems provide boundaries for safe flight with an alerting (amber) awareness and a warning (red) commands. Amber level voice alerts are associated with amber lights, Red levels with a red light and where enabled, terrain-map pop-up depending on system type.
The red warning level requires executive action and is to pull-up wings level to establish the best rate of climb. Wings level has been subject to great debate, which in the early days of EGPWS involved all manufacturers, and the manoeuvre had to correspond with the terrain database/map accuracy. It is likely that as systems have developed, particularly with T2CAS, that in some circumstances a turn might be allowed, but always remember it is terrain (obstacles) that have to be avoided.
Amber cautionary alerting covers many scenarios and generally provides additional time for manoeuvre (but don’t depend on specific time values), - quickly evaluate the situation and adjust. Thus procedure wording can involve flight-path adjustment, climb, GA, turn, or change of configuration.
If a TERRAIN alert is given during an approach then a GA would be the better course of action as the EGPWS and procedures are designed such that alerts should not occur; if they do something is wrong and it is better to establish what at a safe altitude.
TERRAIN alerts at other times might be quickly resolved with flight path adjustment, but don't prejudge any situation assesment.
Other alerts during the approach such as Glide Slope or those involving Flap/Gear, might be subject to operator procedures, but in general the better option is to climb to provide time for evaluation.
Never try to second guess the situation; EGPWS reliability is now significantly better than the rate of human error – EGPWS is an error detector, yours or someone else’s.
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Dozy you are incorrect on so many levels and I do not have sufficient available time on this planet to tell you why. Go and read the fcom
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@tubby linton:
It'd help if you let me know which one I'm supposed to be looking at. If the procedure indeed states "full back stick", then depending on how long the stick is held back that will eventually have a very different effect depending on the FC law.
(And incidentally, I did state that I was in effect making a guess!)
It'd help if you let me know which one I'm supposed to be looking at. If the procedure indeed states "full back stick", then depending on how long the stick is held back that will eventually have a very different effect depending on the FC law.
(And incidentally, I did state that I was in effect making a guess!)
I cannot see that you were guessing from your post. Read the Fcom (there is only one) and you will read how the control laws change and the appropriate procedures. The fctm will also be of interest.
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My apologies, I was hoping the phrases "I would imagine" and "you'd likely be" would indicate that I wasn't certain.
Right, but the link you gave me requires individual downloads of the sections, and it's quite laborious and time-consuming. I have a (kindly donated) complete set of FCOM docs kicking around on a CD-ROM somewhere, but it's still in a box from a recent move, and I don't have time to dig it out.
For a non-pilot, I'm fairly conversant in the Airbus FBW control laws - and the point I was trying to get at was some clarification regarding vilas and sonicbum's assertion that:
specifically regarding how long to hold the stick back for.
Because, if I understand it correctly, when the stick is held back in Normal Law with TOGA power applied, then the High AoA Protection will allow the stick to be held back indefinitely, whereas outside of Normal Law (i.e. Alternate/Direct/Abnormal Attitude) then it is possible to pull the aircraft into a stall if you hold the stick back for too long.
Therefore I assumed it likely that "you must apply TOGA and full back stick", if that is indeed what the manuals say, would have caveats in such conditions.
I didn't think such an assertion would be obviously incorrect...
Read the Fcom (there is only one) and you will read how the control laws change and the appropriate procedures. The fctm will also be of interest.
For a non-pilot, I'm fairly conversant in the Airbus FBW control laws - and the point I was trying to get at was some clarification regarding vilas and sonicbum's assertion that:
...if you get a warning you must apply TOGA and full back stick...
Because, if I understand it correctly, when the stick is held back in Normal Law with TOGA power applied, then the High AoA Protection will allow the stick to be held back indefinitely, whereas outside of Normal Law (i.e. Alternate/Direct/Abnormal Attitude) then it is possible to pull the aircraft into a stall if you hold the stick back for too long.
Therefore I assumed it likely that "you must apply TOGA and full back stick", if that is indeed what the manuals say, would have caveats in such conditions.
I didn't think such an assertion would be obviously incorrect...
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Hey guys, this was my thread! 
Safetypee said:
That is more or less what I was thinking. I consider GPWS as a thing that saves you from yourself. A tool that gives you a chance to get away after you screwed it badly or some faulty or wrongly designed equipment was about to kill you. In approach, a those alerts require a go around, IMHO. As for the other situation other than approach… That is more complex.
Shouldn't "adjust flight path" mean always "climb away, you are way too low"?
I find the wording of this procedure lacking clarity
Safetypee said:
If a TERRAIN alert is given during an approach then a GA would be the better course of action as the EGPWS and procedures are designed such that alerts should not occur; if they do something is wrong and it is better to establish what at a safe altitude.
TERRAIN alerts at other times might be quickly resolved with flight path adjustment, but don't prejudge any situation assesment.
Other alerts during the approach such as Glide Slope or those involving Flap/Gear, might be subject to operator procedures, but in general the better option is to climb to provide time for evaluation.
Never try to second guess the situation; EGPWS reliability is now significantly better than the rate of human error – EGPWS is an error detector, yours or someone else’s.
TERRAIN alerts at other times might be quickly resolved with flight path adjustment, but don't prejudge any situation assesment.
Other alerts during the approach such as Glide Slope or those involving Flap/Gear, might be subject to operator procedures, but in general the better option is to climb to provide time for evaluation.
Never try to second guess the situation; EGPWS reliability is now significantly better than the rate of human error – EGPWS is an error detector, yours or someone else’s.
Shouldn't "adjust flight path" mean always "climb away, you are way too low"?
I find the wording of this procedure lacking clarity
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The caveat in FCOM is that with protections lost (DIRECT LAW), you must respect the stall warning - i.e. reduce the AoA, and fly VSW.
In that sense the actual procedure you would apply is broadly the same as Boeing - i.e. pitch up to stick shaker onset if required, and fly VSW.
In that sense the actual procedure you would apply is broadly the same as Boeing - i.e. pitch up to stick shaker onset if required, and fly VSW.
In that sense the actual procedure you would apply is broadly the same as Boeing - i.e. pitch up to stick shaker onset if required, and fly VSW.
I think it is a good idea to decide now, in the comfort of your lounge ( or hotel room) , to carry out the escape procedure if you get the warning and are in IMC or at night. The reason I say this is that these warnings are disregarded for long periods of time, sometimes until terrain contact, because the pilots have lost SA.
You shouldn't make a judgement call about whether or not to carry out the escape procedure simply because the time you need it, your judgement is faulty. If your SA is fine and you get the warning and carry out the procedure, no worries, good practice and you are justified by the warning.
My two cents.
Microburst, sometimes a "terrain terrain" warning can be fixed with a minor adjustment to the flight path. If so there is no need to do a full blown escape procedure. You need to use judgement.
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A caution such as too low flaps, glideslope, don't sink obviously don't need a GA. All you do is correct the configuration and GS. However about terrain etc or in doubt about SA you should execute GA. As I said before after a caution is sounded you have 60 seconds to impact.
A caution such as too low flaps, glideslope, don't sink obviously don't need a GA. All you do is correct the configuration and GS. However about terrain etc or in doubt about SA you should execute GA. As I said before after a caution is sounded you have 60 seconds to impact.
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Well, yes, but that's exactly what I mean. I take the GPWS as something that will warn me that my situational awareness is not as good as I thought. Once I doubt my SA I have to go away from terrain.
By the way, TOO LOW FLAPS is a go around, according to the procedure. You are really low if you hear that and you still don't have the flaps…
The TOO LOW TERRAIN is what you get when you are not so low yet, but you are very low indeed. If you are too low you did something wrong, like busting a minimum altitude or something. Go away, I say. I guess there are scenarios where a TOO LOW TERRAIN or a TERRAIN TERRAIN do not require a go around or climb initiation, specially when in VMC daylight, but I bet most of the times the best course of action is go around or climb.
By the way, TOO LOW FLAPS is a go around, according to the procedure. You are really low if you hear that and you still don't have the flaps…
The TOO LOW TERRAIN is what you get when you are not so low yet, but you are very low indeed. If you are too low you did something wrong, like busting a minimum altitude or something. Go away, I say. I guess there are scenarios where a TOO LOW TERRAIN or a TERRAIN TERRAIN do not require a go around or climb initiation, specially when in VMC daylight, but I bet most of the times the best course of action is go around or climb.